1. Field of the Invention
The invention relates to an apparatus for reproducing a digital information signal recorded in slant tracks on a longitudinal record carrier in a trick play reproduction mode, the record carrier being transported in said trick play reproduction mode with a speed which equals n times a nominal reproduction speed, n being a constant larger than 1.
2. Description of the Related Art
Such an apparatus is known from U.S. Pat. No. 5,579,183, Document D1 in the List of Related Documents, and International Patent Application No. WO 95/28061, corresponding to U.S. Pat. Nos. 5,751,889 and 6,118,922, Document D2 in the List of Related Documents.
In order to scan the trick play segments as correctly as possible, a tracking control is present for controlling the record carrier transport speed in such a way that the scanning traces of the heads that scan the record carrier during successive revolutions of the head drum cross the trick play segments as accurately as possible.
An objection of the invention is to provide an improved tracking control during a trick play reproduction mode. The apparatus in accordance with the invention, for reproducing a first digital information signal recorded in slant tracks on a longitudinal record carrier in a trick play reproduction mode, the record carrier being transported in said trick play reproduction mode with a speed which equals n times a nominal reproduction speed, n being a constant whose magnitude is larger than 1, said tracks comprising a main signal recording portion in which sync blocks of information are recorded, the main signal recording portion comprising sync blocks having a portion of information of said first digital information signal stored in them and comprising sync blocks having a portion of a second digital information signal stored in them, said second digital information signal being a signal for reproduction in another reproduction mode, such as a reproduction mode with said nominal reproduction speed, said sync blocks of information further comprising:
track identification information, identifying the tracks in subsequent groups of a fixed number of subsequent tracks,
sync block identification information, identifying the sync block in the sequence of sync blocks in said main signal recording portion of a track,
said sync blocks comprising a portion of information of the first digital information signal being recorded in trick play segments located at various locations in said main signal recording portions in said tracks,
the apparatus comprising:
read means for reading information from said record carrier, said read means comprising at least a first and a second read head having mutually different azimuth angles located on a rotatable head drum,
transport means for transporting the record carrier with a specified speed,
tracking control means for carrying out a tracking control during reproduction in said trick play reproduction mode in response to a tracking control signal, so as to enable reading of information from said trick play segments, the tracking control means comprising means for generating a tracking error signal from said track identification information and said sync block identification information, and means for deriving said tracking control signal from said tracking error signal, whereby the tracking control means is adapted to control the speed of the record carrier in such a way that the path that a head follows across the record carrier during one revolution of the head drum is controlled towards a reference path for said trick play reproduction mode across said record carrier, said reference path enabling optimal reproduction of information from said trick play segments for said trick play reproduction mode.
The invention is based on the recognition that tracking in a trick play reproduction mode should be realized on the basis of the track identification information and the sync block identification information comprised in the sync blocks present in the tracks. Those sync blocks need not necessarily be the sync blocks present in the trick play segments corresponding to the said trick play reproduction mode, but can be all the sync blocks present in the tracks. As a result, a very short lock-in time period is required to correctly track the heads on the trick play segments, this time period being defined as the time period between the time instant of switching the apparatus in the trick play reproduction mode and the instant that a picture is present on a TV screen.